1. Technical Field
The present disclosure relates to oil pans made of resin.
2. Background Art
Conventional power units such as engines and automatic transmissions are provided with oil pans for temporarily reserving oil circulated in the power units (see, for example, Japanese Patent Publications Nos. 2-264109 and 2006-283617). An oil pan described in Japanese Patent Publication No. 2-264109 includes an oil reservoir having a bottom wall and a peripheral wall rising from the periphery of the bottom wall. An opening through which oil circulated in a power unit flows into the oil reservoir is formed at the top of the oil reservoir. A plurality of ribs and a fastening portion fastened to the power unit are provided in the oil reservoir, and are located closer to the outside than the opening of the oil reservoir.
An oil pan described in Japanese Patent Publication No. 2006-283617 is formed out of a resin material, and includes an oil reservoir having an opening located in an upper portion thereof.
Further, in an oil pan described in Japanese Patent Publication No. 2003-222012, an oil pan separator is provided in the oil pan to divide an oil reservoir into a main chamber and a sub-chamber such that oil which has circulated in the power unit and returned to the oil reservoir flows into the main chamber (where this oil will be referred to as return oil hereinafter), and that the oil in the main chamber is sucked. With this configuration, when the oil has high viscosity immediately after a cold start, relatively warm return oil which has flown in the main chamber circulates in each part of the power unit, and the temperature of the oil in the main chamber is increased at an early stage, thereby reducing the viscosity thereof. Consequently, friction can be reduced, resulting in reduction of energy consumption.
However, the oil pan of Japanese Patent Publication No. 2006-283617 is formed out of a resin material. Accordingly, the oil pan can have a lighter weight than a steel-made oil pan, but might have insufficient rigidity. In particular, the presence of the opening in the oil reservoir considerably reduces rigidity. Insufficient rigidity of the oil pan might cause each part of the oil pan to easily vibrate with vibration of the power unit, thereby producing noise. In addition, deformation and damage are likely to occur upon application of external forces.
To solve the foregoing problems, a technique of providing a rib for reinforcement as described in Japanese Patent Publication No. 2-264109, is conceivable. However, this rib is provided outside the opening of the oil reservoir, and thus the outer size of the oil pan increases to an extent corresponding to the area of the rib. In addition, even if the rib is provided outside the opening, the opening is still large, and thus considerable reinforcement cannot be expected.
Further, an oil strainer is provided in the oil pan, and various components are provided outside the oil pan in some cases. Thus, the shape of the oil pan needs to be adjusted so as to prevent interference among these components. Moreover, the bottom wall of the oil pan needs to be shaped to allow oil reserved therein to be guided to a suction port of the oil strainer. For these reasons, the shape of the oil pan tends to be complicated.
If such an oil pan is to be formed as one piece made of resin, as described in Japanese Patent Publication No. 2006-283617, the resultant structure thereof is very complicated, and in some cases, oil pan intended to have some shapes cannot be formed.
The oil pan of Japanese Patent Publication No. 2003-222012 includes an additional oil pan separator in order to divide the oil reservoir into a main chamber and a sub-chamber. In this oil pan, the number of parts constituting the oil pan increases, leading to an increase in cost.
It is therefore a first object of the present disclosure is to obtain a compact structure ensuring high rigidity by devising ribs in a resin oil pan.
A second object of the present disclosure is to ensure high rigidity while forming an oil pan of a resin material even when the oil pan is intended to have a complicated shape.
A third object of the present disclosure is to reduce cost by dividing an oil reservoir into a main chamber and a sub-chamber, while enhancing rigidity of the resin oil pan without an increase in the number of parts of the oil pan.